1. Field of the Invention
The present invention relates, in general, to internal combustion engines, and in particular, to a device for rearranging the camshaft of an internal combustion engine.
2. Background Art
A typical internal combustion engine includes an engine block, a plurality of pistons reciprocatingly mounted within cylinders in the engine block, a crankshaft coupled to the pistons for being rotated by the reciprocation of the piston, and a camshaft rotatably driven by the crankshaft of the engine through either a belt drive (commonly called a timing belt) or a chain drive (commonly called a timing chain), etc. As the camshaft rotates, cam lobes fixed to the camshaft push directly or indirectly against rocker arms that press down on cylinder valves (i.e., the intake, or admission, and exhaust valves), causing the valves to open. Further rotation of the camshaft allow springs to return the valves to closed position. The design of the cam lobes (e.g., the profile and position of the cam lobes) determine, among other things, when the valves open, the length of time the valves are held open, etc.
In a standard four-stroke cycle engine, a single cycle of operation (intake, compression, power, and exhaust) takes place over four strokes of a piston, made in two crankshaft revolutions. When a piston is at the top of the cylinder at the beginning of the intake stroke, the intake valve opens and the descending piston draws in the air-fuel mixture. At the bottom of the stroke, the intake valve closes and the piston starts upward on the compression stroke. Just before or as the piston reaches the top again, the compressed air-fuel mixture is ignited by the firing of a spark plug, etc., forcing the piston down on its power stroke. As the piston reaches the bottom of its stroke, the exhaust valve opens, allowing combustion products to be forced out through the exhaust valve.
Some internal combustion engines use dual camshafts, one to operate the intake (admission) valves and the other to operate the exhaust valves. Both of the camshafts in a dual camshaft engine can be driven by a single crankshaft-powered chain drive or belt drive, etc.
The performance of an internal combustion engine can be improved by changing the positional relationship of a camshaft relative to the crankshaft. For example, the camshaft can be xe2x80x9cretardedxe2x80x9d for delayed closing of intake valves or xe2x80x9cadvancedxe2x80x9d for early closing of intake valves. In a dual-camshaft engine, retarding or advancing the camshaft can be accomplished by changing the positional relationship of one of the camshafts, usually the camshaft that operates the intake valves of the engine, relative to the other camshaft and the crankshaft. Accordingly, retarding or advancing the camshaft varies the timing of the engine in terms of the operation of the intake valves relative to the exhaust valves, or in terms of the operation of the valves relative to the position of the crankshaft.
Certain internal combustion engines manufactured by Honda (Honda Giken Kogyo Kabushiki Kaisha of Tokyo, Japan) include an electronic and mechanical system to vary the valve timing. Such engines (called VTEC or Variable Valve Timing and Lift Electronic Control engines) have an extra intake cam and associated rocker. The extra cam is designed to keep the intake valve open longer than the standard cam. At low engine speeds, the extra rocker is not connected to any valve. At high engine speeds, some means secures the extra rocker to the rockers that control the intake valves.
Some internal combustion engines manufactured by Ferrari (Ferrari S.p.A. of Modena, Italy) include means to advance the valve timing to selectively cause the valves to open and close later. For example, if the intake valves normally open at 10 degrees before top dead center (TDC) and close at 190 degrees after TDC, the Ferrari mechanism can open the valves at 10 degrees after TDC and close the valves at 210 degrees after TDC. This is done with a cam lobe having a profile that varies along its length. At one end of the cam lobe is the least aggressive cam profile, and at the other end is the most aggressive. The valve timing is changed by sliding the camshaft laterally so that different parts of the cam lobe engages the rocker arm, etc.
Other manufacturers are reportedly working with systems using a solenoid on each valve to open and close that valve under computer control rather than using a camshaft, etc.
Nothing in the known prior art discloses or suggests the present invention. More specifically, nothing in the known prior art discloses or suggests a camshaft rearranging device including first means for fixed attachment to the camshaft of an internal combustion engine so that rotation of the first means will cause the camshaft to rotate; second means for being rotated by the crankshaft of the internal combustion engine; and third means joining the first and second means to one another so that the first means will rotate when the second means is rotated by the crankshaft and for rotating the first means relative to the second means to rearrange the positional relationship of the camshaft relative to the crankshaft.
The present invention is a camshaft rearranging device for an internal combustion engine including a crankshaft and a camshaft having a longitudinal axis. The camshaft rearranging device of the present invention includes first means for fixed attachment to the camshaft of an internal combustion engine so that rotation of the first means will cause the camshaft to rotate; second means for being rotated by the crankshaft of the internal combustion engine; and third means joining the first and second means to one another so that the first means will rotate when the second means is rotated by the crankshaft and for rotating the first means relative to the second means to rearrange the positional relationship of the camshaft relative to the crankshaft.
It is an object of the present invention to allow the driver of a motor vehicle to vary the valve timing of the engine so as to maximize engine performance at different RPM""s.
It is another object of the present invention to allow the driver of a motor vehicle to so vary the valve timing by rotating the camshaft a few degrees relative to the crankshaft. For example, if the intake valves of the engine of a motor vehicle normally open at 10xc2x0 before top dead center (TDC) and close at 190xc2x0 after TDC, for total open duration of 200xc2x0, the present invention allows the driver to rotate the camshaft ahead a few degrees relative to the crankshaft, thereby shifting the opening and closing times so that the valve might open at 10xc2x0 after TDC and close at 210xc2x0 after TDC.